“What should I eat on race day?” This is probably one of the most common question asked of sports dietitians and coaches by athletes. My answer is, “tell me what you eat everyday.” Probably not the response you were expecting. But it does make you stop and wonder how dietary habits and nutrition contributes or even impacts endurance performance.

What, when, why and how much one eats during the months of training leading up to race day has everything to do with what and how often the body requires energy in the form of calories, specifically carbohydrates (or as we call it in the field of sports nutrition, “fuel”) on race day. Moreover, the composition of ones macronutrient intake (meaning, the ratio of carbohydrates to proteins) plays a key role in building a broad and efficient aerobic foundation and metabolism. The efficiency enhances usage of fats (fatty acids) for energy, optimizes body composition, and can improve one’s weight and overall health! Now that’s sustainability!

When I first began racing triathlon in 2000 (Wildflower Long Course being my first!), there was one general rule of thumb to follow: eat carbs! In fact, eat up to 60% of your daily diet as carbohydrates. Carbs were king! And so I ate, we ate, carbohydrates, lots of them, all the time. Personally, this eventually led to an increase in hunger, weight, fatigue, GI distress during racing, and poor recovery. I learned a lot that first year.

Fast forward to 2018, triathletes seasoned and new are dipping into the low-carb/high-fat, Paleo, and nutritional ketosis diet approaches. With so many approaches, which is the best approach to follow?

Whether your goal is to PR or simply cross your first finish line, understand that your dietary habits and food choices during the aerobic base phase of training have everything to do with race day performance. That’s because there are three times as many opportunities to nail your nutrition in the day than there are to train.

The “25/75” Rule. Nutrition is 75 percent of the performance, body composition and health equation; training is the remaining 25 percent. Let’s break down what this means.

Training 25%. The purpose of establishing an aerobic foundation is to create a “base” from which to build sustained strength, speed, and power in the weeks and months that follow. During this phase, intensity is low, what my athletes relate to as “embarrassingly slow” with a few, not many, high-intensity intervals. “Training low” improves upon the body’s aerobic endurance and fat-max. This is, the maximum amount of fats (fatty acids) the body burns at a specific intensity over time. How much and at what point ones maximal fat utilization occurs is highly individual. It is influenced by both training and nutrition.

Improving individual fat-max improves one’s “crossover” point, or as Bob Seebohar, MSc, RD, CSSD notes, a “Metabolic Efficiency Point” (MEP, Figure 1). That is, the point in which the body uses both carbohydrates and fats equally. With just the right amount of intensity and a few tweaks to the diet, the crossover point or MEP shifts to the right leading to more efficient metabolism; the body burns fats (stored in an abundant supply) and spares precious stores of carbohydrate (muscle glycogen and blood glucose). That’s an efficient body and what Bob Seebohar, MSc, RD, CSSD calls, “Metabolic Efficiency”.

“Hitting the Wall” or “Bonking” are terms used to describe when the body’s carbohydrate supply runs low. You feel tired, irritable, unable to focus or concentrate, and the muscles even stop firing – there’s just no oomph!

Nutrition 75%. Let’s face it – you eat more often through the day than train. As a result, blood sugar (glucose) levels rise and fall. Blood glucose is most influenced by the type and amount of carbohydrate eaten (Figure. 2). Control of blood sugar with regard to the hormone insulin improves endurance performance, body composition, satiety, and overall health. (High protein intake, above the body’s protein needs, can also cause a rise in blood sugar, but we’ll save that topic for another blog post.)

→ Key Point! When blood glucose rises as a result of consuming carbohydrate rich foods the body secretes insulin, a hormone responsible for transporting the glucose into the cell to be used or stored as energy. The release of insulin blunts the body’s ability to burn fats and focuses on carbohydrate metabolism: fats are stored, carbs are burned. Even more, circulating insulin is correlated to increased hunger.

In laymen’s terms, eating carbohydrate-laden meals and snacks (including processed, “whites”, added sugars, and sugar substitutes) raises blood sugar. What goes up must come down – and hits rock bottom. What happens next is a desire for a “pick-me-up”. And who has ever reached for a stalk of broccoli to improve energy and satiety. Right?

The more carbohydrates consumed the greater the body’s need for insulin. The more often insulin is secreted, the greater the risk of diabetes, high cholesterol, high blood pressure, cardiovascular disease…the list goes on and on. Triathletes are not immune to disease – and, we eat a lot!

In Summary. what we’re taking about here pertains to year-round daily nutrition for not only building an efficient aerobic foundation, but to also control weight and enhance body composition through the metabolisms efficient use of fats as fuel (over carbohydrates), while reducing the risk of disease!

Whether your approach is low-carb/high-fat, Paleo or Keto (nutritional ketosis), bare in mind that carbohydrates play a key role in “fueling” the muscles and brain during quality training and race day performance. Sure, being in nutritional ketosis has its benefits (which I’ll discuss in a later blog), but when it comes to being at your performance best, carbs are still king – or queen – at the right time and in the right amounts.

If you are the type to preload with a gel or carbohydrate drink 15 minutes before and/or again 30 to 45 minutes into a 60 to 75 minute aerobic run, then your body is carbohydrate dependent. If you are able to sustain yourself for 60 to 75 minutes or longer for aerobic training, then you’ve been doing your work…and there’s always room for improvement!

“So what do I eat for daily nutrition?” Great question! Coming right up – stay tuned!!